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Checking the Numbers: Power Sapped

An anomaly is defined as a strange discrepancy or deviation from an established trend or baseline. In baseball terms, they occur when teams or players defy expectations—in either direction—to the extent that it proves difficult to offer confident explanations. Take, for instance, the 57 home runs on Luis Gonzalez’s resume under the 2001 heading: Gonzo was a solid hitter, but 57 dingers? Tallies like that are generally reserved for the cloutiest of cloutsmen, and not a player perennially ranging from 17-25 homers.

On the opposite end of this spectrum stands David Wright, the Mets' third baseman with all the makings of a Hall of Fame career, but who experienced an anomaly for the ages last season in the power department. While many have worked diligently to unearth the cause of his decline in power output, I am more interested in the historical ramifications—has a player with as established of a power baseline ever experienced a similar dropoff? And, if so, is there enough of a precedent to help fuel or modify expectations moving forward?

Wright hit 10 home runs last year in what was, for all intents and purposes, a full season of playing time. That's right, 10! After averaging 29 dingers per season from 2005-08, Wright’s bopping of just 10 long balls would be akin to Ichiro batting .264, Roy Halladay posting 4.47 ERA, or the Royals acquiring a batter whose OBP exceeds .319. It just isn’t bloody likely, and it can drive fans batty searching for causes. Was it the new Citi Field and its dimensions (not likely, as park effects would account for a dropoff of, at most, three or four homers)? A change in swing mechanics or in hitting philosophy? A lingering injury? Or, perhaps, a decision to mail it in until Omar Minaya signed more backup catchers? Whatever the cause, it was particularly peculiar that he sustained talent in the midst of being sapped for power, as Wright hit .307/.390, a BA and OBP virtually identical to his PECOTA forecast, but with a .447 SLG that more closely resembled what one might expect from teammates Daniel Murphy or Fernando Tatis.

Determining if Wright has any company in this regard does not involve too much heavy lifting, and the method I employed is more back of the envelope than anything else as well. I started by isolating any season from 1873-2009 in which a hitter amassed 300 or more at-bats. Next, I calculated the average tally and standard deviation of home runs hit, broken down by league and year. For instance, qualifying hitters in the 1982 AL averaged 14.92 blasts with a standard deviation of 9.79; it could be approximated that about two-thirds of these players ranged from 5-24 home runs. The next step was to compute the z-score for each player season, which is simply the number of standard deviations from the mean a data point strays. Reverting to our handy-dandy 1982 AL example, Tom Brunansky’s 20 home runs for the Twins turned out to be 0.52 standard deviations from the mean.

From there, I manipulated the results to show a five-year span in each row, since Wright’s power dropoff occurred in the fifth year of a similarly long span of seasons. A grand total of 6,267 five-year spans emerged, but in order to determine if Wright has any peers, I needed to find a commonality amongst his personal numbers. The table below shows Wright’s pertinent data from 2005-09:

Looking at the z-score column, the commonality is that his home run total in each season either met or exceeded the average by 0.65 standard deviations. Leafing through the data for players who similarly bopped for the first four years returned 821 spans, but here comes the kicker: When I search for players meeting the aforementioned benchmarks but who fell to -0.60 or more standard deviations below the mean in the fifth season, a grand total of five rows are returned. Five! Over the last 150 years or so, there have literally only been a handful of players to experience a power dropoff from a previously established and high baseline of hitting home runs. The Oceanic Five:

What initially stands out is Wright was only 26 years old last season while the other cast members were 31 years of age or older. Another fantastically curious factoid is that the other four players barely surpassed the at-bats minimum in that fifth year, ranging from 322-340, while Wright surpassed the 500 mark. Both of these are points in favor of Wright’s anomalous season being about as rare as rare can be in this sport.

If I loosen the fifth year parameter to be less than or equal to -0.40 standard deviations below the mean, the sample barely grows to 14 five-year spans. No matter how I choose to slice the numbers, it is evident that Wright’s season is of bizarro-world status. Even with the additions to the sample, Wright still turns out to be the youngest by a fairly wide margin, which suggests that what happened to him last year is unprecedented in baseball history. No other player has been as productive from a home run standpoint at such a young age, for a four-year stretch, who suddenly turned into Juan Pierre (exaggeratory, sue me!) from a power perspective, while playing full seasons.

Now, sure, I may have been a bit liberal with my querying criteria, but if I loosen it over the first four years, the largest sample I can produce while satisfying the integrity of an attempt to find comparables is 21 spans. Among those 21 spans, only one non-Wright player was around the same age in his bizarro power season: Dusty Baker—yeah, him—who averaged around 19 HR/year from 1972-75 as a member of the Braves before bopping a grand total of four home runs in his first season in Dodger blue. Baker only played in 112 games in that 1976 season, but that does not explain the entirety of his dramatic decrease in home runs. Maybe he threw his arm out.

Luckily for Wright, Baker quickly regained his power, averaging 23 homers per year for the next four seasons. Regardless of what I set as the searching criteria, examining what "similar" players did in the next year or two, which would equate to the sixth and seventh years in a span, proves futile, as most did not even amass 300 or more at-bats after their power plummet, and only a couple went on to once again bash. The samples are so small, however, that their successes (or lack thereof) should in no way drive what to expect from Wright moving forward. PECOTA largely agrees, and a fun exercise is to compare his actual 2010 projection to what his 2009 PECOTA card forecasted for the 2010 season.

The actual 2010 projection pegs Wright’s weighted mean at .313/.415/.541, compared to the 2009 projection of 2010 which had him at .305/.405/.543. Simply put, PECOTA is very bullish on Wright moving forward and appears to be dismissing his 2009 power output, thinking it to be immaterial to what Wright is capable of moving forward. The anti-Brady Anderson in every sense of the term, there are few reasons to expect Wright to continue last year’s putrid power output. Something definitely happened last season to cause such a vast decrease, but searching through the annals of history reveals very, very few comparables from even a broad perspective, indicating that his 2009 campaign was not only anomalous, but literally unprecedented.

In all likelihood, fans a decade from now will look back at his 10-homer season as a blip on an otherwise fantastic career consisting of many more 30-plus dinger years, and in a few weeks, when live regular-season baseball once again occupies our time and Wright looks like the player of years past, few will even think about what happened last season.

My takeaway from your research, Eric, differs a little from yours. You've demonstrated to my satisfaction that Wright's 2009 power drop has no comparable precedent. It's a black swan. As such, I think we need to be very careful when assessing any forecast of Wright's future at this point.
Anyone who wants to believe his 2010 PECOTA is certainly free to do so, but should at the same time recognize that there must be a tremendous amount of risk associated with that forecast, since we're treading on fresh powder here.

I could agree with this if there were any discovered reason for the drop in power. I'm sure Mets fans and people in the organization know more than I do, but I have yet to hear a solid theory about what happened. As that is the case, it makes good sense to assume that the man will continue hitting the way he always has, especially since power was the only area where he suffered last season.

I disagree 100%. The fact that there isn't a discovered reason for the loss of power is precisely why one should be worried. If something of historic preportions happens and we don't understand why, then why should we be comfortable sweeping it under the rug and writing it off as an aberration?

Moreoever, since PECOTA is a projection system based on historical context, and you've just demonstrated that there's no historical context for what Wright has done, PECOTA is probably the wrong tool for this job. I'll go with guessing, in keeping with the Mets' general human resources strategy.

Very-well written.
The modern example is Gary Gaetti. Given that he's still fresh in many minds, I'm more curious as to what happens when you relax the 'years' criteria. I'd certainly think "3 years of boppin' followed by a cliff dive" is similar enough to merit extrapolation from. What happens then? Even 2 might be worth a look-see while including an age qualifier.

I suppose one thing you should've given us is, did the old dudes regain their power, or how much. If they did, then we can deductively figure the younger Wright ought to also.
Likewise, if the 3-years guys did, that would be a plus. Also so for the similarly-aged 2-years guys.

Can't respond directly when at work, but Richie, I did include that. I mentioned that only a handful of the guys even played into a 6th and/or 7th season (or didn't amass 300+ ABs in those seasons) and only a couple of them regained power. Which tells us little because the sample is so small and even less because the sample shrinks the further out we extrapolate.

Excellent article.
Mean reversion is one of the most powerful forces at work when we examine series of data over time. There is a strong tendency for the average of something to be the average, unless there is a new element introduced that can explain why a historic average level of something should not be expected going forward.
In addition to injury, lack of lineup protection, and new ballpark, I wonder if a look at batted balls in play would shed some light. I recall the Kevin Youkilis a season or two ago had a number of "just barely made it" home runs -- is it possible that Wright last season had a far higher number of "just barely missed" balls -- either fly balls that were caught at the wall, or line drives of flies that went off the wall for doubles?
A look at a change in Wright's ground ball - line drive - fly ball performance last year compared to his career might be informative.
I agree with the reader about the implications of this black swan. The problem with making a bet on mean reversion in this instance is that it is very difficult to pin down the cause of the power drop, which makes having confidence that 2009 was "just an outlier" problematic. For fantasy purposes, players will have to weigh the liklihood and magnitude of mean reversion against the "implied" recovery of either draft position or auction value. To take a page out of the capital markets, Wright's sudden (and largely unexplained) spike in "beta" should cause rational investors to charge a higher risk preimum for him in 2010 in the form of drafting him later or paying less for him at auction than normally would be the case.
The other question in my mind is the validity of saying "well, Dusty Baker bounced back, so Wright likely will too." I think this assertion might suffer both from small sample size, and from the idea that the conditions surrounding the two players are very different.
All that said, I find it hard to believe that short of injury being the root cause, that Wright suddenly lost "power" as a skill, and my hunch is a good "over-under" line on his home runs for 2010 is around 25-26-27 . .

Glad you enjoyed it. I of course never said that Dusty Baker's post-suckiness success was concrete evidence that Wright will improve. It was more tongue in cheek: hey, one other guy had this happen and he got better, so boom! There are several potential factors for the dropoff, but I wanted to focus more on the historical precedents aspect, which hadn't yet been tackled, partly because searching for the reasons can drive one nuts.

Eric, do you see any similarities between Wright's career path and George Brett's? Brett didn't establish the same kind of power base Wright did, obviously, but he'd been steadily building to a power peak at 27 -- then took a big step backwards at 28, and only approached his mid-20s level twice again in his career.
Not that I think Mets fans will mind if Wright has a George Brett kind of career ...

In 2009, Wright's walks dropped from 94 to 74, while his strikeouts increased from 118 to 140 (total plate apps were down from 735 in 2008 to 613 in 2009). On a percentage basis, K's went from 16.05% of plate apps to 22.84%, a pretty big increase.
So, one theory might be that for whatever reason, Wright's plate discipline (or lack thereof compared to prior seasons) was a material factor in his decline in power production -- fewer walks and more strikeouts could be symptomatic of Wright chasing many more borderline pitches, which are much harder to square up and hit out of the park.
Wright's HR's on balls in play fell from a career avg of 5.47% thru 2008 to 2.53% in 2009.
What is also interesting is that Wright's numbers during the prior 4 seasons appear to show far less year to year natural variance than most players who get 600-700 PA's; that makes the sudden power drop all the more notable.

Interesting article. Eric, I'm wondering your thoughts on Wright hitting more balls to the opposite field, as Derek Carty wrote about on THT yesterday. It would seem that there was a definite change in approach.

It definitely seems that way. When I started formulating this I had to battle whether I wanted to discuss potential reasons for the dropoff or if it had ever occurred before. Obviously, the latter won out so I didn't spend much time with my Dr. Gregory House cap on, but I am certainly in the camp that he did something different last season. Perhaps he psyched himself out as to the dimensions of the stadium and tried to go to the opposite field more often. Or maybe it just sort of happened. It's just fascinating that it happened to begin with. Unfortunately, what we'd really need to know in this case is what happens to players who start pushing the ball more often in the years following that season and I'm not sure we have accurate enough data for that yet.

Prob. the most relevant stat (not mentioned here) is his HR/FlyBall rate. It plunged to 6.9% last year (vs. 13.9% for his career). His FB rate (best predictor of future HR rate) was 35.9% last year vs. 38.9% overall -- certainly a drop, but not massive. Citi Field has a pretty normal HR/FB rate overall, so this looks primarily to be a fluke.

According to Greg Rybarczyk of hit tracker, Wright lost 9 homers that would have gone out of Shea and in general the team lost a great deal. The park effect number for last year is most likely due to bad luck that the Mets and especially their opponents had with hitting homers on the road last year and will likely go down significantly after we have another sample in 2010. Note that the overall number of homers for Mets and their opponents was very low last year.
If Wright has 30 homer power this year, he could again lose half of them to the ballpark and end up with 15.

In order to lose half your home runs "to the ballpark," the ball park would have to allow no home runs to anyone. Not only is this obviously untrue, but Citi field had a HR/FB park factor of 98 last year -- essentially neutral, and an overall HR park factor of 106.
Unless you assume that a player's precise flyball distribution (locations where his FBs land) repeats year-to-year, there is no reasonable way to assume that Citi will continue to have a dramatic negative effect on Wright.

This is pretty obvious... If it is agreed a guy would hit 30 HR in a neutral environment, and someone claims due to his actual environment he will hit 15 HR, it means his home park (where half the games are played) is being assumed to allowed zero HR. Not that tough to understand.

Eric,
Interesting article, but Wright's decline is not totally unprecedented; the same type of power outage was experienced by Bobby Murcer in 1974, ironically, when he moved from Yankee Stadium to Shea Stadium during the renovation of the Bronx ballpark.
Murcer's HR totals from 1969-1973 were an impressive (given the era in which he played) 26,23,25,33, and 22. Murcer's power suddenly vanished, as he tallied only 10 dingers in his lone year at Shea Stadium, thus precipitating his unexpected and unpopular departure for San Francisco.
The bad news for Mets fans hoping Wright's power collapse was simply a fluke - Murcer's HR troubles followed him to the west coast, as he managed a paltry 11 round-trippers the following season. The good news; Murcer inexplicably suddenly rediscovered his long-ball stroke in 1976, belting 23 HRs for the Giants - who immediately celebrated his resurgence by trading him to the Cubs, where he belted another 27 homers in 1977.
But at that point age began catching up to Murcer, and, though he remained a HR threat throughout the remainder of his career, his gradual demotion to the status of a part-time player meant his days of producing gaudy HR numbers were over.

Murcer wouldn't have shown up here because he had 5 years of good power before the dropoff and the database query involved finding four years. I'm going to run through everything again this weekend to see if I can find 5 yrs then dropoff like Murcer.

Just checked Murcer -- the problem with using him as a comparable is that in YR5, David Wright was -0.60 SDs below the mean for his league/year. Murcer, while meeting the criteria for the first 4 years, was only -0.11 SDs below the mean in that fifth year. So from a raw tally standpoint, yes, Murcer had a good amount of HRs and then fell off in the fifth year, but from this method, which is used to normalize league/year differences, his fifth year was actually right in line with the average whereas Wright was a good amount below the average.

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